You think probable to powders or granules of material.
Ceramic
Mortar is what is used to stick bricks together.
Mortar is used to stick bricks together.
A bricklayer or bricky
Builder
Beth
Insulators.
Those bricks are called adobe. (ah-doh-bee)
fired. lol
If it's plywood, it's probably at least 3/4 real ply as opposed to 3/4 composite, what I call Japanese wood. However, I wouldn't use ply under ceramic tile. I would use at the very least the material called Hardi-Board. Ask about it at the hardware store.
If you have an oil or gas fired furnace, you may have a cracked plenum, in which case you may be getting exhaust inside the house. Call a specialist right away.
Call him in to your office and say, "You're fired!"